题目内容
若x=| 1 |
| 2 |
| a |
| b |
| 1 |
| 2 |
| a |
| b |
分析：直接代入再合并同类二次根式．
解答：解：x+y=
(
+
)+
(
-
)=
（
+
+
-
）=
×2
=
．
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点评：本题考查了二次根式的加减运算，注意要先代入再化简．
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若x=| 1 |
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（2013•南漳县模拟）如图，△ABC中，点O是边AC上一个动点，过O作直线MN∥BC．设MN交∠ACB的平分线于点E，交∠ACB的外角平分线于点F